Preheat grill to 400 degrees.
In a large bowl, gently toss peaches, tomatoes, peppers and red onion with grapeseed oil.
Place fruit and vegetables on greased grill and cook until lightly browned.
Bring grilled ingredients to room temperature before chopping into small pieces.
Rinse fish fillets in water and pat dry.
Arrange fillets in a shallow dish, brush with grapeseed oil and sprinkle with salt and pepper.
In a large bowl, whisk together vinegar, lime juice, garlic, salt and pepper.
Add grilled fruit and vegetables, tomatoes and cilantro, tossing until combined.
Place fish fillets on the grill and cook at medium-high for approximately 3 minutes per side or until fish flakes easily with a fork.
Serve halibut immediately with a side of peach salsa.