diff --git a/.github/workflows/CI.yml b/.github/workflows/CI.yml
index 20f1e83..b38d34d 100644
--- a/.github/workflows/CI.yml
+++ b/.github/workflows/CI.yml
@@ -44,19 +44,10 @@ jobs:
       - uses: julia-actions/install-juliaup@5e96cfab3bb0500aa42f2843f46c24b91cfcc3cd
         with:
           julia-version: "1.10.2"
-      - run: |
-          juliaup default 1.10.2
-          juliaup add 1.10.1
-
-      - run: julia +1.10.1 --project=test/multiversion/envs/CommonMark_1.10.1 -e 'import Pkg; Pkg.instantiate()'
-        env:
-          JULIA_PKG_PRECOMPILE_AUTO: "0"
-
-      - run: julia +1.10.2 --project=test/multiversion/envs/CommonMark_1.10.2 -e 'import Pkg; Pkg.instantiate()'
-        env:
-          JULIA_PKG_PRECOMPILE_AUTO: "0"
+      - run: juliaup default 1.10.2
 
       - run: julia --project -e 'import Pkg; Pkg.instantiate()'
+      - run: julia --project -e 'import PackageBundler; PackageBundler.instantiate("test/multiversion/envs")'
       - run: julia --project test/multiversion/bundle.jl
 
       - uses: actions/upload-artifact@5d5d22a31266ced268874388b861e4b58bb5c2f3
@@ -145,12 +136,7 @@ jobs:
           version: ${{ matrix.version }}
       - uses: julia-actions/cache@dc1a3cdeacb521b0ca93cfc66143fcadb15a5bd0
       - uses: julia-actions/julia-buildpkg@90dd6f23eb49626e4e6612cb9d64d456f86e6a1c
-
-      # `PackageBundler.bundle()` expects the environments to be bundled to have
-      # already been instantiated (hence downloaded) prior to running it. We
-      # don't need to precompile it though.
-      - run: julia --project=test/envs/CustomEnv -e 'ENV["JULIA_PKG_PRECOMPILE_AUTO"]=0; import Pkg; Pkg.instantiate()'
-
+      - run: julia --project -e 'import PackageBundler; PackageBundler.instantiate("test/envs")'
       - uses: julia-actions/julia-runtest@79a7e100883947123f8263c5f06e6c0ea3eb972f
       - uses: actions/upload-artifact@5d5d22a31266ced268874388b861e4b58bb5c2f3
         with:
diff --git a/src/PackageBundler.jl b/src/PackageBundler.jl
index 81f917d..4a2e60a 100644
--- a/src/PackageBundler.jl
+++ b/src/PackageBundler.jl
@@ -289,5 +289,6 @@ end
 
 include("openssl.jl")
 include("code_stripping.jl")
+include("utilities.jl")
 
 end # module PackageBundler
diff --git a/src/utilities.jl b/src/utilities.jl
new file mode 100644
index 0000000..93472c1
--- /dev/null
+++ b/src/utilities.jl
@@ -0,0 +1,73 @@
+"""
+    instantiate(environments::String)
+
+Scan the directory `environments` for subdirectories containing a
+`Manifest.toml` file and instantiate them all using the appropriate `julia`
+version as specified in the `Manifest.toml` file. This uses either `juliaup` or
+`asdf` to switch between `julia` versions as needed. Make sure to have either of
+those installed, as well as the expected `julia` versions.
+"""
+function instantiate(environments::String)
+    if ispath(environments)
+        if isfile(environments)
+            error("The path '$environments' is a file, not a directory.")
+        end
+    else
+        error("The path '$environments' does not exist.")
+    end
+    for each in readdir(environments; join = true)
+        manifest = joinpath(each, "Manifest.toml")
+        if isfile(manifest)
+            @info "Instantiating $each"
+            toml = TOML.parsefile(manifest)
+            julia_version = toml["julia_version"]
+            if !isnothing(Sys.which("juliaup"))
+                @info "Checking whether Julia '$julia_version' is installed, if not, installing it."
+                run(`juliaup add $julia_version`)
+                withenv("JULIA_PKG_PRECOMPILE_AUTO" => 0) do
+                    run(
+                        `julia +$(julia_version) --project=$each -e 'import Pkg; Pkg.instantiate()'`,
+                    )
+                end
+            elseif !isnothing(Sys.which("asdf"))
+                # Using the `ASDF_JULIA_VERSION` environment variable to control the
+                # `julia` version used doesn't appear to have an effect. Instead
+                # compute the exact path to the binary and use that instead.
+                asdf_dir = get(
+                    ENV,
+                    "ASDF_DATA_DIR",
+                    get(ENV, "ASDF_DIR", joinpath(homedir(), ".asdf")),
+                )
+                if isdir(asdf_dir)
+                    julia_path = joinpath(
+                        asdf_dir,
+                        "installs",
+                        "julia",
+                        "$(julia_version)",
+                        "bin",
+                        "julia",
+                    )
+                    if !isfile(julia_path)
+                        @info "Installing Julia '$julia_version', since it does not appear to be installed."
+                        run(`asdf install julia $julia_version`)
+                    end
+                    if isfile(julia_path)
+                        withenv("JULIA_PKG_PRECOMPILE_AUTO" => 0) do
+                            run(
+                                `$julia_path --project=$each -e 'import Pkg; Pkg.instantiate()'`,
+                            )
+                        end
+                    else
+                        error(
+                            "The `julia` binary for version $julia_version failed to install.",
+                        )
+                    end
+                else
+                    error("`asdf` is not installed in a known location. $asdf_dir")
+                end
+            else
+                error("`asdf` or `juliaup` is required to instantiate the environments.")
+            end
+        end
+    end
+end
\ No newline at end of file