Can I freeze stir-fry vegetables?
You will have the best results if you prep by cutting and blanching prior to freezing. This should ensure that moisture content in the veggies does less damage over time in the freezer and improve color duration. I find it helpful to freeze vegetables separately rather than as mixes as you can always grab from multiple bags, but you can't unmix mixed vegetables without more work.

The majority of vegetables for stir-fry (e.g. broccoli, peas, etc) will freeze well enough, the ones in your freezer aisle obviously freeze a bit better than others. If a vegetable has a high water content (i.e. lettuce, which I hope you aren't stir-frying with) that is more integral to its structure than the cellulose it is likelier to burst cell walls in freezing; these vegetables are better to avoid.