M Query: Add list of months between dates

Hi, Anonymous , don't bother to use List.Generate(); List.Accumulate() would come in handy in your senario. You might want to try,

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMlTSUTLRN9Q3MjC0BDKN9Y1BbCMDpVidaCUjoIgZRNICyDRFSMYCAA==", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [ID = _t, award_begin_date = _t, award_end_date = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"ID", Int64.Type}, {"award_begin_date", type date}, {"award_end_date", type date}}),

    #"Added Custom" = Table.AddColumn(
        #"Changed Type",
        "col",
        each 
        let
            begin = Date.StartOfMonth([award_begin_date])
        in
            List.Accumulate(
                {0..(Date.Year([award_end_date])-Date.Year([award_begin_date]))*12+(Date.Month([award_end_date])-Date.Month([award_begin_date]))},
                {},
                (s,c) => s&{Date.AddMonths(begin,c)}
            )
    ),

    #"Expanded col" = Table.ExpandListColumn(#"Added Custom", "col")
        
in
    #"Expanded col"