Heat peanut oil in a large nonstick skillet or wok over medium-high heat. Add broccoli and bell peppers; cook, stirring often, until tender-crisp, about 6 minutes. Add scallions, chiles (or crushed red pepper), garlic and ginger; cook, stirring, until fragrant, about 30 seconds. Reduce heat to low, add the reserved sauce mixture and cook, stirring, until thickened, about 30 seconds. Remove from heat and stir in peanuts.